LXR qemu/slirp/cksum.c

   1/*
   2 * Copyright (c) 1988, 1992, 1993
   3 *      The Regents of the University of California.  All rights reserved.
   4 *
   5 * Redistribution and use in source and binary forms, with or without
   6 * modification, are permitted provided that the following conditions
   7 * are met:
   8 * 1. Redistributions of source code must retain the above copyright
   9 *    notice, this list of conditions and the following disclaimer.
  10 * 2. Redistributions in binary form must reproduce the above copyright
  11 *    notice, this list of conditions and the following disclaimer in the
  12 *    documentation and/or other materials provided with the distribution.
  13 * 3. Neither the name of the University nor the names of its contributors
  14 *    may be used to endorse or promote products derived from this software
  15 *    without specific prior written permission.
  16 *
  17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27 * SUCH DAMAGE.
  28 *
  29 *      @(#)in_cksum.c  8.1 (Berkeley) 6/10/93
  30 * in_cksum.c,v 1.2 1994/08/02 07:48:16 davidg Exp
  31 */
  32
  33#include <slirp.h>
  34
  35/*
  36 * Checksum routine for Internet Protocol family headers (Portable Version).
  37 *
  38 * This routine is very heavily used in the network
  39 * code and should be modified for each CPU to be as fast as possible.
  40 *
  41 * XXX Since we will never span more than 1 mbuf, we can optimise this
  42 */
  43
  44#define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
  45#define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1];        \
  46        (void)ADDCARRY(sum);}
  47
  48int cksum(struct mbuf *m, int len)
  49{
  50        register uint16_t *w;
  51        register int sum = 0;
  52        register int mlen = 0;
  53        int byte_swapped = 0;
  54
  55        union {
  56                uint8_t  c[2];
  57                uint16_t s;
  58        } s_util;
  59        union {
  60                uint16_t s[2];
  61                uint32_t l;
  62        } l_util;
  63
  64        if (m->m_len == 0)
  65           goto cont;
  66        w = mtod(m, uint16_t *);
  67
  68        mlen = m->m_len;
  69
  70        if (len < mlen)
  71           mlen = len;
  72#ifdef DEBUG
  73        len -= mlen;
  74#endif
  75        /*
  76         * Force to even boundary.
  77         */
  78        if ((1 & (uintptr_t)w) && (mlen > 0)) {
  79                REDUCE;
  80                sum <<= 8;
  81                s_util.c[0] = *(uint8_t *)w;
  82                w = (uint16_t *)((int8_t *)w + 1);
  83                mlen--;
  84                byte_swapped = 1;
  85        }
  86        /*
  87         * Unroll the loop to make overhead from
  88         * branches &c small.
  89         */
  90        while ((mlen -= 32) >= 0) {
  91                sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  92                sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
  93                sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
  94                sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
  95                w += 16;
  96        }
  97        mlen += 32;
  98        while ((mlen -= 8) >= 0) {
  99                sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
 100                w += 4;
 101        }
 102        mlen += 8;
 103        if (mlen == 0 && byte_swapped == 0)
 104           goto cont;
 105        REDUCE;
 106        while ((mlen -= 2) >= 0) {
 107                sum += *w++;
 108        }
 109
 110        if (byte_swapped) {
 111                REDUCE;
 112                sum <<= 8;
 113                if (mlen == -1) {
 114                        s_util.c[1] = *(uint8_t *)w;
 115                        sum += s_util.s;
 116                        mlen = 0;
 117                } else
 118
 119                   mlen = -1;
 120        } else if (mlen == -1)
 121           s_util.c[0] = *(uint8_t *)w;
 122
 123cont:
 124#ifdef DEBUG
 125        if (len) {
 126                DEBUG_ERROR((dfd, "cksum: out of data\n"));
 127                DEBUG_ERROR((dfd, " len = %d\n", len));
 128        }
 129#endif
 130        if (mlen == -1) {
 131                /* The last mbuf has odd # of bytes. Follow the
 132                 standard (the odd byte may be shifted left by 8 bits
 133                           or not as determined by endian-ness of the machine) */
 134                s_util.c[1] = 0;
 135                sum += s_util.s;
 136        }
 137        REDUCE;
 138        return (~sum & 0xffff);
 139}
 140